We present a novel method that robustly estimates the reflectance, even in an environment with dynamically changing light. To control the appearance of an object by using a projector-camera system, an appropriate estimate of the object's reflectance is vital to the creation of an appropriate projection image. Most conventional estimation methods assume static light conditions; however, in practice, the appearance is affected by both the reflectance and environmental light. In an environment with dynamically changing light, conventional reflectance estimation methods require calibration every time the conditions change. In contrast, our method requires no additional calibration because it simultaneously estimates both the reflectance and environmental light. Our method is based on the concept of creating two different light conditions by switching the projection at a rate higher than that perceived by the human eye and captures the images of a target object separately under each condition. The reflectance and environmental light are then simultaneously estimated by using the pair of images acquired under these two conditions. We implemented a projector-camera system that switches the projection on and off at 120 Hz. Experiments confirm the robustness of our method when changing the environmental light. Further, our method can robustly estimate the reflectance under practical indoor lighting conditions.

With projection mapping, we can control the appearance of real-world objects by adding illumination. A projector can be used to control light reflected from an object, where the reflected light depends not only on the projection but also on the reflectance and environmental light. Because the resulting colors are affected by the reflectance and environmental light, the presentable color range of a projector is limited. The purpose of this work is to broaden this limited range by focusing on the perceived colors. Although our eyes capture reflected light to perceive the colors of an object, the colors perceived by humans are not always the same as the actual colors, and there are often significant differences between them because of the human visual system. To overcome the limitations of a projector based on human perception, we intentionally generate this difference by inducing a visual illusion, namely, color constancy. In this work, we designed an algorithm to determine the projected colors for presenting the desired colors perceptually by employing a color constancy effect. In addition, we conducted a user study and confirmed that our algorithm can (1) create a misperception regarding the color of illumination, (2) broaden the presentable color range of a projector, and (3) shift the perceptual colors in the desirable direction.

Using projection mapping, we can control the appearance of realworld objects by projecting colored light onto them. Since a projector can only add illumination to the scene, limited color gamut can be presented through projection mapping. However, actual color and perceived color are not always the same, and there is often large difference between them. We intentionally generate this difference by inducing visual illusion for extending the controllable color gamut of a projector. In particular, we induce color constancy. We demonstrate changing object color with and without inducing color constancy. Audiences perceive the controlled colors with and without illusion as different color nevertheless these colors are physically completely same.

Using projection mapping, we can control the appearance of realworld objects by projecting colored light onto them. Because a projector can only add illumination to the scene, only a limited color gamut can be presented through projection mapping. In this paper we describe how the controllable color gamut can be extended by accounting for human perception and visual illusions. In particular, we induce color constancy to control what color space observers will perceive. In this paper, we explain the concept of our approach, and show first results of our system.